首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
To fight a noise by making more noise sounds strange ,but that’s exactly what motor engineers are doing in Germany and some othe
To fight a noise by making more noise sounds strange ,but that’s exactly what motor engineers are doing in Germany and some othe
admin
2009-05-15
49
问题
To fight a noise by making more noise sounds strange ,but that’s exactly what motor engineers are doing in Germany and some other countries.
Car makers’ research and development laboratories have already proved that mixing more noise with the help of loudspeakers can reduce the unwanted noise.
Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency(频率) mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore ,by producing a perfect copy of the noise and delaying it by half a wave cycle(周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems(系统)both inside and outside the cars.
Another good thing about the use of noise-killing systems is that it saves the need for a silencer; this not only reduces the weight of a car, but also makes the motor burn less fuel and work better.
Some engineers believe that the noise-killing system will be used in most cars within a few years. But the carmakers haven’t decided if they will carry it into production because it would add several hundred dollars to the cost of their cars.
选项
A、By producing pressure waves going in the opposite direction.
B、By mixing high frequency sound waves with low frequency sound waves.
C、By mixing new sound waves with the noise and sending them out together.
D、By making copies of the unwanted sound waves and letting them out a little later.
答案
D
解析
从文章第三段第四句:Therefore,by producing a perfect copy of the noise and delaying it by half a wave cycle,we can kill the unwanted noise.得。故本题答案为D。
转载请注明原文地址:https://kaotiyun.com/show/FGyd777K
本试题收录于:
公共英语二级笔试题库公共英语(PETS)分类
0
公共英语二级笔试
公共英语(PETS)
相关试题推荐
Onedaytwoscientistswerequarrellingaboutwhosewatchwasbetter,theGermanoneortheJapaneseone.Sincetheywerescient
Severalpassageswerefound______whenthebook______me.
Animationmeansmakingthingswhicharelifelesscomealiveandmove.Sinceearliesttimes,peoplehavealwaysbeenastonish
StudentsinStateUniversities______iftheirparentsliveinthatstate.Nearlyhalfofallcollegestudents______whilethe
Takingtileplaceofteachingforaneighth-gradeclass,Inoticedthatmanyofthestudentswereaskingforpermissiontoleave
Jack’smotheraskedhimtomovethefamilypianofromthediningroomtothelivingroom.Hewasstrong,butnotstrongenought
ThevisitingMinisterexpressedhissatisfactionwiththetalks,______thathehadenjoyedhisstayhere.
Infact"trickortreat"is______.Withinonlyoneweek,______.
Themurdererwasbroughtin,withhishands______behindhisback.
随机试题
直肠长度约为
下列关于优先股与普通股说法错误的是()。
马斯洛理论中的人类需求包括:()。
下列选项中,属于夜间行车存在安全隐患的原因的是()。
下列我国古代绘画理论名句所表达的美学理念与其他三项不同的是:
ItwasnotuntilI______yourletterthatI______allaboutthematter.
Lookatthestatementsbelowandatthefiveextractsfromanarticleaboutlossofcontroldownwardinmanagement.Whicharticl
ComputerMonitoringismostoftenintendedtoimproveefficiencyandeffectivenessintheworkplace,butwithgoodintentionsco
A、Helppeoplechangetheirfeelingsaboutoldage.B、Revealthatoldpeoplearepoor,lonelyandunhappy.C、Leadpeopletofind
Manycriticsconsiderthatfarmorestressisplacedonachievementsinathleticsthanintheacademicsphere.We’retoldthati
最新回复
(
0
)